This is a Home Office Circular dated 12th May, 1969 and is called Informants who take part in crime.
Documents of this nature are usually released into the public domain - via the Public Record Office (or the National Archives if you really must) - after thirty years. I received it from a Home Office official named Alan Robinson. I have a feeling this correspondence was related to an attempt to set me up by bent coppers (who believing their own lie ridden propaganda incited me to commit a murder). Anyone who is skeptical of this claim should read my dissertation Al-Qaeda In Britain: Does The Secret State Lend A Hand? (see url below).